As traffic mainly of voice changes to traffic mainly of video or data, demanded is to flexibly accommodate packets in a transport network which transmits traffic in a wide range.
One of networks meeting such a demand is a hybrid network in which packets and paths exist together. Possible hybrid networks include a network formed of a packet network which aggregates packets from a user and a wavelength network which cuts through traffic between packet switches.
Example of such a hybrid network is shown in FIG. 14. The hybrid network shown in FIG. 14 is formed of an Ethernet network 1100 and a wavelength network 1200 and includes a packet switching unit (Ethernet switch) 1000-i (i=1, 2, . . . ). an optical switching unit (optical switch) 1001-j (j=1, 2, . . . ) and a user device 1002-k (k =1, 2, . . . ). The Ethernet switch 1000 and the optical switch 1001 are here structured as a single communication device having two kinds of switch functions in some case or as separate communication devices in other case.
In a communication system having such a structure, for linking two different networks, it is a common practice to set a connection of a wavelength path and communicate with a connectionless type Ethernet network by using the set wavelength path.
Example of related art of such a linkage method on a network is recited, for example, in Patent Literature 1. The linkage method recited in Patent Literature 1 operates to determine whether a cut-through path should be created or not by setting a wavelength path between a transmission source address SA (transmission end) and a destination address DA (reception end) with respect to an Ethernet traffic transfer path based on a traffic flow. Because of the following problems, such a system, however, fails to realize autonomous linkage between a connection type communication network and a connectionless type communication network.
Patent Literature 1: Japanese Patent Laying-Open No. 2004-328727 (pp. 9-12, FIG. 3 and FIG. 6).
First problem is that it is impossible to find a new destination MAC address (MAC-DA) on an Ethernet network.
The reason is that because an Ethernet broadcast packet is transferred along an already set wavelength path, no broadcast packet reaches a destination MAC address (MAC-DA) to which no wavelength path is connected. For example, in the structure shown in FIG. 14, when traffic is transferred with the Ethernet switch 1000-1 as a transmission source address SA and the Ethernet switch 1000-4 as a destination MAC address (MAC-DA), the destination MAC address (MAC-DA) of the Ethernet switch 1000-4 cannot be found because arrival through a wavelength path is impossible (i.e. no linkage on the Ethernet network).
Second problem is instability of a network. The reason is that because determination is made on setting/deletion of a new wavelength path based on a traffic flow, when the volume of traffic changes heavily, setting/deletion of a wavelength path occurs frequently to change a network topology of the Ethernet frequently.
(Object of the Invention)
An object of the present invention is to provide a network communication system, a communication device, and network linkage method and program which realize automatic and stable network operation in a network having connection type communication and connectionless type communication existing together.